The present technology relates to orifice plate wellhead systems and, in particular, orifice plate wellhead systems configured to easily determine and/or adjust the flow rate of fluid.
Most landfill gas is produced by biodegradation, which occurs when organic waste is broken down by bacteria naturally present in the waste and in the soil used to cover the landfill. Landfill gas is mostly made of methane, carbon dioxide, and trace amount of a wide variety of volatile organic compounds.
Landfill gases can contribute to ozone formation, atmospheric photochemical reaction, and other types of air pollution. Landfill gases can also create dangerous conditions. For example, if methane is present in the air at higher concentrations, it can be explosive. Landfill gases may also contribute to water pollution if it migrates and comes in contact with groundwater. Therefore, it is desirable to collect landfill gas to prevent these dangers. Collected landfill gases can be used as a source of power generation, or be incinerated before being released into the atmosphere.
Active landfill gas well extraction systems are used to collect landfill gases. Such systems are commonly made of an array of pipes and valves in fluid communication with a vacuum source. Active landfill gas well extraction systems also include wellhead assemblies, which are used to monitor and control the amount of gas passing through the pipes. A wellhead assembly can include flow rate measurement sensors and a flow rate control feature, which are used to determine and control the gas extraction rate.
One of the important considerations in using a gas well extraction system is to precisely control the gas flow rate. Under-extraction rates mean the extraction rate is not high enough to prevent gas from reaching the surface or prevent subsurface migration. This may result in air pollution or a fire hazard. Over-extraction rates mean the extraction rate is high enough to draw large amounts of air into the waste column. This may kill many of the microorganisms, resulting in reduced methane recovery. Thus, the gas flow rate needs to be carefully monitored and controlled within a narrow operating range to prevent over- or under-extraction of landfill gas.